The pulsatile secretion of gonadotropin-releasing hormone (GnRH) is the key regulator of reproduction. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are differently regulated by different pulse frequencies of GnRH. The goal of this proposal is to determine the mechanism of regulation of LH and FSH gene expression by pulsatile GnRH. Specific Aim 1: Determine Pulse Frequencies Determine the GnRH pulse frequencies that lead to maximal expression of LH beta and FSHbeta genes utilizing transient transfection for short-term pulsatile treatment and stable transfection for longer pulsatile treatment in the L beta T2 gonadotrope cell line. Specific Aim 2: Determine Signaling Cascades Determine the signal transduction pathways necessary for the induction of LHbeta versus FSHbeta genes by pulsatile GnRH. Determine which signaling molecules are activated by specific pulse frequencies and compare their activation to tonic GnRH. Specific Aim 3: Determine the Transcriptional Mechanisms Determine the promoter regions and transcription factors that play roles in pulsatile GnRH induction of the LHbeta and FSHbeta genes. Identify new target genes for pulsatile GnRH using DNA microarray approaches.